1. Field of the Invention
The present invention relates generally to a method and apparatus for allocating resources in a wireless communication system, and in particular, to a method and apparatus for adaptively allocating fragmented resources using a virtual resource space to avoid the degradation of system performance caused by the fragmented resources.
2. Description of the Related Art
Providing services with diverse Quality of Service (QoS) requirements at or above 100 Mbps to users is an active study area for a future-generation communication system called a 4th Generation (4G) communication system. Particularly, research is being conducted on the provisioning of high-speed service by ensuring mobility and QoS to Broadband Wireless Access (BWA) communication systems such as Wireless Local Area Network (WLAN) and Wireless Metropolitan Area Network (WMAN). A major example of these systems is an Institute of Electrical and Electronics Engineers (IEEE) 802.16e system.
As illustrated in FIG. 1, the IEEE 802.16e communication system notifies each Mobile Station (MS) of radio resources allocated to it by MAPs in every frame. For downlink resource allocation, a two-dimensional position and size resource allocation scheme is used which specifies the frequency-axis start point and length of allocated resources or the time-axis start point and length of the allocated resources, and for uplink resource allocation, a one-dimensional length resource allocation scheme is applied which indicates only the length of allocated resources.
If many users want to be allocated a small amount of radio resources periodically for a predetermined time period, like Voice over Internet Protocol (VoIP) users, transmission of resource allocation information to the users in every frame may increase the size of MAPs too much. Since more resources are taken to transmit the MAP information than actual traffic information, system inefficiency results.
To avert the problem of an increased MAP size, a periodic allocation scheme has been proposed in which radio resources are allocated periodically rather than on a frame basis. The periodic allocation scheme gives authorization to users to use radio resources of other frames as well as radio resources of a current frame. For instance, as illustrated in FIG. 2, radio resources A 220 in a kth frame 201, radio resources A 222 in a (k+1)th frame 203, and radio resources A 224 in a (k+2)th frame 205 are allocated to user 1 by a MAP in the kth frame 201. Therefore, user 1 can use all of radio resources A 220, 222 and 224 without further resource allocation by MAPs in the (k+1)th frame 203 and the (k+2)th frame 205.
The above-described periodic allocation scheme obviates the need for resource allocation frame by frame, thus reducing the overhead of MAPs. However, since the start position and size of the allocated radio resources are indicated for resource allocation, resources are fragmented and the fragmented resources are not available for allocation. Referring to FIG. 3, when radio resources 310 are allocated to user 5 in a (k+3)th frame 301, not enough radio resources 312 to be allocated to a user may remain between the radio resources 310 and radio resources 314 allocated to user 3.
The fragmented small-size radio resources are not available for allocation to a user in the conventional resource allocation scheme. Accordingly, there exists a need for developing a method for overcoming the radio resource fragmentation, while reducing the overhead of MAPs.